More lives were lost, as Americans chose driving
over flying

By Robert Preer

In the months after the terrorist attacks of September 11, 2001,
Americans shunned airports and instead, took to the nation’s
highway — presumably on the belief that vehicular travel was a safer
option. Yet what seemed a better bet ended up costing more lives,
because travelers shifted to a more dangerous mode of transportation,
according to research by Johnson professor of marketing and
economics Vrinda Kadiyali.

"Because of extra
security measures,
fewer people choose to
fly, and when they drive
instead of flying, more
people die on the road."

-Professor Vrinda Kadiyali

“After controlling for observable and unobservable factors that
influence fatalities, we estimate that as many as 2,300 lives were
lost, because of travelers’ response to 9/11,” write Kadiyali and her
co-authors, Garrick Blalock and Daniel H. Simon of Cornell’s
Dyson School of Applied Economics and Management, in “Driving
Fatalities After 9/11: A Hidden Cost of Terrorism,” published in
Applied Economics, Vol. 41, Issue 14, 2009. “These deaths are a
hidden cost of the 9/11 attacks.”

Travelers appear to have avoided flying not only because they
thought it was safer but also because they wanted to avoid delays
and hassles associated with increased airport security, according to
the researchers.

“These extra security measures are imposed to tell people that it
is safer to fly,” Kadiyali says. “But, because of those measures, fewer
people choose to fly, and when they drive instead of flying, more
people die on the road.”

The researchers analyzed data on all motor vehicle fatalities in
the U.S. between 1994 and 2003. Highway deaths increased significantly
after 9/11, the researchers found. To isolate the so-called “9/11 effect” the researchers used statistical analysis to control for variations in air fares and general economic conditions.

They also compared data on fatalities involving commercial
vehicles — primarily trucks transporting cargo — and non-commercial
vehicles, such as passenger cars. If a 9/11 effect did exist,
there would be higher death rates for non-commercial vehicles, since
commercial vehicles would be on the road, regardless of terrorism
fears, the researchers hypothesized. In fact, the researchers found
that fatalities involving commercial vehicles did not increase after
9/11, while deaths involving non-commercial vehicles spiked.

They also identified several additional signs of a 9/11 effect. Outof-
state fatalities increased more than in-state fatalities — evidence
that travelers substituted highway for air travel. And fatalities went
up most in the Northeast, where typical travel distances are shorter
and driving is an attractive alternative to flying.

Also, the increase in auto deaths weakened
over time, with fatalities returning to pre-9/11 levels
by October 2003. According to the researchers, this
probably happened because fear of flying lessened, and
travelers adjusted to airport security measures.

But in the two years the 9/11 effect held sway,
more than 2,000 people died on the nation’s highways,
according to Kadiyali.

“When we did the calculation and found
the number, my heart sank,” she says. “Look at how
imperfectly we make decisions and what the cost can
be, when we improperly assess risk.”